Assays are often used for chemical or biochemical analysis. Typically a sensor is coated with an immobilized receptor species (e.g., an antibody), and detection of target species (e.g., antigens) corresponding to the immobilized receptor is performed by sensing bound target-receptor complexes with the sensor. A wide variety of sensor and sensing technologies have been employed in such applications. One such approach is electrochemical impedance spectroscopy, where the bound target-receptor complexes alter an electrical impedance of the sensor. Characterization of this impedance change (typically vs. applied electrical frequency) provides the desired assay signal. In some cases, the sensitivity of an electrochemical impedance spectroscopy is lower than desired. Accordingly, it would be an advance in the art to provide improved electrochemical impedance spectroscopy for chemical and/or biochemical assays.